If the directive has a default value (i.e., if you omit it
from your configuration entirely, the Apache Web server will behave as
though you set it to a particular value), it is described here. If
there is no default value, this section should say
"None".

This indicates where in the server's configuration files the directive
is legal. It's a comma-separated list of one or more of the following
values:

server config

This means that the directive may be used in the server
configuration files (e.g., httpd.conf,
srm.conf, and access.conf), but
not within any <VirtualHost> or
<Directory> containers. It is not allowed in
.htaccess files at all.

virtual host

This context means that the directive may appear inside
<VirtualHost> containers in the server
configuration files.

directory

A directive marked as being valid in this context may be used
inside <Directory>,
<Location>, and <Files>
containers in the server configuration files, subject to the
restrictions outlined in How Directory,
Location and Files sections work.

.htaccess

If a directive is valid in this context, it means that it can
appear inside per-directory .htaccess files.
It may not be processed, though depending upon the
overrides
currently active.

The directive is only allowed within the designated context;
if you try to use it elsewhere, you'll get a configuration error that
will either prevent the server from handling requests in that context
correctly, or will keep the server from operating at all --
i.e., the server won't even start.

The valid locations for the directive are actually the result of a
Boolean OR of all of the listed contexts. In other words, a directive
that is marked as being valid in "server config,
.htaccess" can be used in the httpd.conf file
and in .htaccess files, but not within any
<Directory> or <VirtualHost> containers.

This directive attribute indicates which configuration override must
be active in order for the directive to be processed when it appears
in a .htaccess file. If the directive's
context
doesn't permit it to appear in .htaccess files, this
attribute should say "Not applicable".

Overrides are activated by the
AllowOverride
directive, and apply to a particular scope (such as a directory) and
all descendants, unless further modified by other
AllowOverride directives at lower levels. The
documentation for that directive also lists the possible override
names available.

This indicates how tightly bound into the Apache Web server the
directive is; in other words, you may need to recompile the server
with an enhanced set of modules in order to gain access to the
directive and its functionality. Possible values for this attribute
are:

Core

If a directive is listed as having "Core" status, that
means it is part of the innermost portions of the Apache Web server,
and is always available.

Base

A directive labeled as having "Base" status is
supported by one of the standard Apache modules which is compiled
into the server by default, and is therefore normally available
unless you've taken steps to remove the module from your configuration.

Extension

A directive with "Extension" status is provided by one
of the modules included with the Apache server kit, but the module
isn't normally compiled into the server. To enable the directive
and its functionality, you will need to change the server build
configuration files and re-compile Apache.

Experimental

"Experimental" status indicates that the directive is
available as part of the Apache kit, but you're on your own if you
try to use it. The directive is being documented for completeness,
and is not necessarily supported. The module which provides the
directive may or may not be compiled in by default; check the top of
the page which describes the directive and its module to see if it
remarks on the availability.

If the directive wasn't part of the original Apache version 1
distribution, the version in which it was introduced should be listed
here. If the directive has the same name as one from the NCSA HTTPd
server, any inconsistencies in behaviour between the two should also
be mentioned. Otherwise, this attribute should say "No
compatibility issues."